Many of drugs, particularly anticancer agents, are sparingly water-soluble hydrophobic compounds. When such drug is used to attain a desired therapeutic effect, the drug is usually solubilized and administered to a patient. Accordingly, solubilization of sparingly water-soluble drugs, particularly sparingly water-soluble anticancer agents, is important for oral or parenteral pharmaceutical preparations, particularly those for intravenous administration.
As one method of solubilizing a sparingly water-soluble anticancer agent, there is a method which comprises adding a surfactant, and it is known to use, for example, a polyoxyethylene castor oil derivative (Cremophor) in order to solubilize paclitaxel. As an another method, a method of using a micelle-forming block copolymer as a drug carrier is described in, for example, JP-A-6-107565 (Patent Document 1), JP-A-6-206815 (Patent Document 2) or JP-A-11-335267 (Patent Document 3), and paclitaxel-encapsulated micelles are described in JP-A-2001-226294 (Patent Document 4).